A typical wireless communication system includes a number of base stations each radiating to provide coverage in which to serve wireless client devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped devices, whether or not user operated. In turn, each base station may sit as a node on a core network including entities such as a network controller and a gateway system that provides connectivity with an external transport network such as the Internet. With this arrangement, a WCD within coverage of the system may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other WCDs served by the base station.
Such a system may operate in accordance with a particular radio access protocol, examples of which include, without limitation, Long Term Evolution (using Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), IEEE 802.11 (WIFI), BLUETOOTH, and others. Each protocol may define its own procedures for registration of WCDs, initiation of communications, handover between base station coverage areas, and other functions.
Further, each base station may provide wireless service to WCDs on one or more carrier frequencies (carriers), each of which could be frequency division duplex (FDD), defining separate frequency channels for downlink and uplink communication, or time division duplex (TDD), defining a frequency channel multiplexed over time between downlink and uplink use. Each carrier or its respective channels could be within a defined frequency band and could be of a particular frequency bandwidth, such as 5 MHz, 10 MHz, or 20 MHz for instance, defining a certain extent of air interface resources.
When a WCD initially powers on within such a system, the WCD may scan various carriers in search of base station coverage, and upon detecting strong enough coverage, the WCD may engage in an access process to establish a radio-link layer connection with the base station, and the WCD may then engage in an attach process through which the system becomes configured to serve the WCD. In an example attach process, for instance, the WCD may transmit an attach request over the air to the base station, and the base station may forward the attach request to the network controller in the core network. After authenticating and authorizing the WCD, the network controller may then then engage in signaling with the base station and with the gateway system, to coordinate and trigger establishment of a network connection for the WCD.
This process may result in setup of a network connection, including at least one bearer (data tunnel), between the WCD and the gateway system via the base station, with a Dynamic Host Control Protocol (DHCP) server assigning to the WCD an Internet Protocol (IP) address usable by the WCD to engage in packet-data communication on the transport network. In particular, the network connection could define a particular access point name (APN) connection that is associated with external transport-network connectivity and communication. Further, the process may result in creation and storage at various core network entities of a context record for the WCD, identifying the WCD's network connection, bearer identity, and other information to facilitate serving the WCD.
Once a WCD is so attached, the base station may then provide the WCD with wireless data communication service. In an example arrangement, for instance, when data arrives on the transport network destined to the WCD's IP address, the gateway system may transmit the data via the WCD's bearer to the base station, and the base station may then schedule downlink air interface resources to carry the data to the WCD and transmit the data to the WCD accordingly. Likewise, when the WCD has data to transmit on the transport network, the WCD may send a scheduling request to the base station, the base station may schedule uplink air interface resources to carry the data from the WCD, and upon receipt of the data at the base station, the base station may then transmit the data via the WCD's bearer to the gateway system for transmission on the transport network.
Further, when a base station operates in such a system, the base station may engage in various types of communication with other core network entities. For instance, the base station could engage in control-plane communication, encompassing encompasses any of the base station's control signaling with other core network entities to help manage operations in the system and service of WCDs, and could thus include communications such as bearer setup signaling, tracking area update signaling, paging, handover signaling, the like. Further, the base station could engage in user-plane communication, encompassing bearer data (e.g., application data, user data, etc.) being communicated to or from one or more WCDs served by the base station, such as packet data that the base station receives from the gateway system and then schedules/transmits to a WCD and packet data that the base station receives from a WCD and forwards to the gateway system for transmission on a transport network.